The present invention relates to an engine mount used for installing an engine on a vehicle body.
In general, when an automobile engine and the like is installed on a vehicle body, engine mounts are interposed therebetween in order to control vibration transmission from an engine to a vehicle body. One prior art example of an engine mount is shown in FIG. 5. Said engine mount comprises a body side metal fitting 101 fixed to a vehicle body, an engine side metal fitting 102 fixed to an engine, a vibration isolating base body 103 formed of a rubber elastic body interposed between both of the metal fittings 101 and 102, and a liquid chamber 104. The engine side metal fitting 102 is provided with a stopper rubber portion 107 substantially in a disc shape protruding radially outwardly from said metal fitting constituted of an outer peripheral flange 105 protruding radially outwardly from said metal fitting and a coating rubber 106 covering the outer periphery of the outer peripheral flange 105. The engine side metal fitting 102 is disposed substantially concentrically with and spaced from the body side metal fitting and the stopper rubber portion 107 is opposed to an inner periphery of the body side metal fitting 101 so as to absorb the impact force generated at the time when a load in a radial direction is applied and prevent the deterioration of riding comfort on a vehicle.
However, since the stopper rubber portion 107 is concentrically disposed at the inside of the body side metal fitting 101, a radius of curvature of the outer periphery thereof is smaller than that of the inner periphery of the body side metal fitting 101. As a result, at the time when a load in the radial direction is applied, the edge of the stopper rubber portion 107 is first brought into contact with a small area of the inner periphery of the body side metal fitting, and thereafter, the contact edge is distorted inwardly to extend gradually the contact area of the stopper rubber portion 107 with the body side metal fitting.
Consequently, the stopper rubber portion 107 is greatly distorted at the edge portion to be first brought into contact with the body side metal fitting 101. Thus, when a radial load is repeatedly applied to the engine mount during vehicle running on a bad road for a long period, it is likely to cause cracks of the stopper rubber portion.
In view of the above, it is an object of the present invention to improve the durability of the stopper rubber portion in an engine mount, and another object of the present invention is to enhance riding comfort by damping a vibration transmitted from the stopper rubber portion to a vehicle body.
In order to attain the above objects, the present invention intends to uniform the distortion of the stopper rubber portion to the utmost by contacting widely the stopper rubber portion with the body side metal fitting at the time when a radial load is applied to the engine mount comprising a cylindrical body side metal fitting secured to a vehicle body, an engine side metal fitting secured to an engine, a vibration isolating base body made of an elastic rubber body interposed between the two metal fittings and a stopper rubber portion substantially in a disc shape protruding radially outwardly from the engine side metal fitting and disposed substantially concentrically with and spaced from the body side metal fitting. xe2x80x9cRadialxe2x80x9d or xe2x80x9cradiallyxe2x80x9d means the direction perpendicular to the axial direction passing through a center of the body side metal fitting. The stopper rubber portion is widely contacted with the body side metal fitting as follows.
Assuming that two radial directions orthogonal to each other in a radial plane perpendicular to the axis of the body side metal fitting are one direction and another direction, respectively, contact parts that contact the inner periphery of the body side metal fitting when a load is applied in one direction are denoted as one-direction contact parts and contact parts that contact the inner periphery of the body side metal fitting when a load is applied in another direction are denoted as another-direction contact parts. In the present invention, a center of curvature of an outer periphery of each one-direction contact part positioned at one direction of two radial directions orthogonal to each other in a radial plane is displaced from a center of curvature of an inner periphery of the body side metal fitting in the one direction and a radius of curvature of the outer periphery is arranged to be larger than a radius of curvature of an imaginary circle passing through a single point of the outer periphery of the stopper rubber portion concentrically with the inner periphery of the body side metal fitting. In such a manner, as compared with such a case that the outer periphery of the stopper rubber portion is arranged to be a circle, i.e. the imaginary circle, concentric with the inner periphery of the body side metal fitting, the one-direction contact parts contact with the body side metal fitting over a wide region and local rubber distortion is diminished. When the radius of curvature of the one-direction contact parts is larger than the imaginary circle, the contact parts contact widely with the inner periphery of the body side metal fitting. However, when the radius of curvature of the one-direction contact parts is larger than the inner periphery of the body side metal fitting, each of the contact areas of the contact parts becomes small. Accordingly, the radius of curvature of the one-direction contact parts shall be arranged to be larger than the imaginary circle and equal to or smaller than the radius of curvature of the inner periphery of the body side metal fitting.
Namely, the present invention provides an engine mount comprising a cylindrical body side metal fitting secured to a vehicle body, an engine side metal fitting secured to an engine, a vibration isolating base body made of an elastic rubber body interposed between the two metal fittings and a stopper rubber portion formed substantially in a disc shape protruding radially outwardly from the engine side metal fitting and disposed substantially concentrically with and spaced from the body side metal fitting. The stopper rubber portion is arranged in such a manner that a center of curvature of an outer periphery positioned at one direction of two radial directions orthogonal to each other in a radial plane being displaced from a center of curvature of an inner periphery of the body side metal fitting to the one direction and a radius of curvature of the outer periphery being arranged to be larger than a radius of curvature of an imaginary circle passing through a single point of the outer periphery of the stopper rubber portion concentrically with the inner periphery of the body side metal fitting and equal to or smaller than a radius of curvature of the inner periphery of the body side metal fitting, so that contact parts contacting with the body side metal fitting in the one direction of two radial directions orthogonal to each other are brought into contact with the body side metal fitting over a wide region.
Especially when the radius of curvature of the one-direction contact parts is arranged to be substantially equal to that of the inner periphery of the body side metal fitting, the entire outer periphery of the one-direction contact parts is brought into contact with the body side metal fitting.
The stopper rubber portion comprises an outer peripheral flange protruding radially outwardly from the engine side metal fitting and a coating rubber covering an outer periphery of said outer peripheral flange. Accordingly, the above-mentioned arrangement of the radius of curvature of the one-direction contact parts corresponds to the arrangement for the outer periphery of the coating rubber.
From the above viewpoint, the configuration of the outer peripheral flange and the rubber thickness of the coating rubber are not required to be limited specifically. However, taking the durability of rubber into consideration, it is preferable that the distortion of rubber at the time when the coating rubber is brought into contact with the inner periphery of the body side metal fitting is made uniform Accordingly, it is preferable that the coating rubber positioned in the one-direction contact parts has a constant thickness in the circumferential direction thereof. In order to obtain said constant thickness, a center of curvature of the outer periphery of the outer peripheral flange positioned at the one-direction contact part is displaced from a center of curvature of an outer periphery of the coating rubber to one direction and a radius of curvature of said outer periphery is arranged to be equal to a radius of curvature of the outer periphery of the coating rubber.
Namely, the present invention also provides an engine mount comprising a cylindrical body side metal fitting secured to a vehicle body, an engine side metal fitting secured to an engine, a vibration isolating base body made of an elastic rubber body interposed between the two metal fittings and a stopper rubber portion substantially in a disc shape protruding radially outwardly from the engine side metal fitting and disposed substantially concentrically with and spaced from the body side metal fitting, the stopper rubber portion is constituted of an outer peripheral flange protruding radially outwardly from the engine side metal fitting and a coating rubber covering an outer periphery of said outer peripheral flange, a center of curvature of said outer periphery of the outer peripheral flange positioned at said contact parts being displaced from a center of curvature of an outer periphery of the coating rubber positioned at said contact parts to said one direction and a radius of curvature of said outer periphery being equal to a radius of curvature of the outer periphery of the coating rubber, so that the coating rubber of the contact parts positioned in said one direction has constant thickness in a circumferential direction thereof.
It is more preferable that the outer periphery of the coating rubber is substantially of a circle shape and the outer periphery of the outer peripheral flange is substantially of an ellipse shape constituting said one-direction contact parts by the outer periphery positioned in the direction of a short diameter of the ellipse. Although the rubber thickness of the another-direction contact parts becomes thin, the rubber thickness of the coating rubber at the one-direction contact parts becomes thick, which makes the riding comfort enhanced.
Namely, the present invention also provides an engine mount comprising a cylindrical body side metal fitting secured to a vehicle body, an engine side metal fitting secured to an engine, a vibration isolating base body made of an elastic rubber body interposed between the two metal fittings and a stopper rubber portion substantially in a disc shape protruding radially outwardly from the engine side metal fitting and disposed substantially concentrically with and spaced from the body side a metal fitting, said stopper rubber portion is constituted of an outer peripheral flange protruding radially outwardly from the engine side metal fitting and a coating rubber covering an outer periphery of said outer peripheral flange, said outer periphery of the outer peripheral flange being formed substantially in an ellipse shape constituting said contact parts positioned in said one direction by the outer periphery positioned in the direction of a short diameter of the ellipse, a center of curvature of said outer periphery of the outer peripheral flange positioned in the direction of a short diameter of the ellipse being displaced from a center of curvature of an outer periphery of the coating rubber to said one direction and a radius of curvature of said outer periphery being equal to a radius of curvature of the outer periphery of the coating rubber, so that the contact parts positioned in said one direction has a constant thickness in a circumferential direction thereof.
Since a load applied to the engine mount in the radial directions thereof orthogonal to each other during the vehicle running is likely to be greater in one direction than in another direction, it is preferred that the above one-direction contact parts are disposed in alignment with said one direction, i.e. a principal load applying direction of the engine mount, so that both the durability of the stopper rubber portion and the riding comfort are enhanced.